Alkylation process



United States Patent 3,004,088 ALKYLATIUN PROCESS John F. Hutto, Bartlesville, Okla., assignor to Phillips Petroleum Company, acorporationof Delaware Filed ct. y11i, 1958, Ser. No. 766,824 4 Claims. (Cl. 260-683.42)

This invention relates to alkylation. In one of its aspects, this invention relates to a process for the alkylation ot' hydrocarbons in which deisoparaflinizer bottoms are reboiled under conditions to cause detluorination of thev same while at the same time there is removed from the deisoparainizer a normal paraffin stream.

Itis well known thatreboiling the deisobutanizer bottoms in an HF alkylation process will substantially deuorinate the alkylate provided suilcient time of heating is given. The residence time required at 400 F. is such that the ratio of feed to the Vreboiler to the net bottoms product is in the neighborhood of approximately 8:1. Such a ratio cannot :be achieved at the temperature required for deuorination when there is a high concentration of normal butane in the kettle product since this normal butane concentration interferes with proper heat balance and equilibrium vaporization which are required for satisfactory operation of the column.

Also, is has been found to be desirable to operate at as high a temperature as possible for maximum delluorination, the upper limit being determined'by the color of the alkylate product (-about 500 F. maximum). With this temperature limitation, it has been found that between 6 to 8, even to l0, volumes of bottoms must be circulated through the bottoms furnace for each volume of bottoms yield to effect suicient contact time for desired deuorination. These conditions, however, provide too much reboiler duty, i.e., heat input (B.t. u.s) for optimum tower operation at the desired tower operating temperature. This condition is governed to a large extent by the quantity of normal butane in the alkylate; i.e., as the normal butane content of the Vbottoms increases, the bubble point of the tower bottoms decreases, and the Vamount of Vaporization in the reboiler `furnace eluent increases.

It has now been conceived that in an HF alkylation of an isoparafln with an olefin, for example, in the alkylation of isobutane with a butane-butylene stream in the presence of hydrouoric acid, the deisobutanizer bottoms should be circulated through a heating zone back to the deisobutanizer while at the same time removing from the deisobutanizer a side stream containing normal butane.

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nating zone maintained at a deuorinating temperature and returning the thus-heated and at least partially defluorinated eluent to said deisoparanizer zone.

The invention will now be described with respect to the alkylation of isobutane with a lbutylene-containing stream in the presence of HF acid. It will be obvious to those skilled in the art in possession of this disclosure that the invention has general applicability to deuorination of streams other than those given in the speciiic example.

Referring now to the drawing, hydroiluoric acid, isobutane and a butylene-containing stream, also containing some butane, are fed by way of conduits 1, 2 and 3 into alkylator 4 from which an alkylation effluent is passed by way of conduit 5 to acid settler 6. Acid from which substantially all desirable hydrocarbon has been separated by settling is passed by way of recycle conduit '7 to conduit 1 for reuse. supernatant hydrocarbon stream is passed by way of conduit 8@ to fractionator 9 from which an overhead of C3 hydrocarbons and lighter is removed by way of conduit 10. Bottoms from fractionator 9 are passed by way of conduit 11 to deisobutanizer 12 from which isobutane-containingl streamis taken overhead by way of conduit13. According to the invention, a normal butane stream is removed from tower 12 by way of conduit 14. Also, -according to the invention, bottoms from the deisobutanizer are withdrawn by way of conduit 15 and pumped by way of pump 16 and conduit 17 into heated coil 1S, which is maintained in this example at approximately 400 F. and from coil 18 by way of pipes 19 and 20 back to the bottom of the deisobutanizer. Production quantities of deiluorinated and deisobutanized alkylate are passed bykconduit 21, valve 22 and conduit The normal butane can be'rernoved from the operation or it can be passed to a debutanizer or otherwise treated as desired. One use Vfor the normal butane is to isomerize the same to isobutane for reuse.

It is an object of this invention to provide an improved alkylation process. lt is another object of this invention to provide an alkylation process in which improved defluorination of deisoparafhnizer bottoms is practiced. It is a further object of this invention to provide an alkylation process in which improved operation of a deisoparafnizer, for example, a deisobutanizer, is obtained while at the same time, deiluorinating the alky-late produced.

Other aspects, objects and the several advantages of the invention are apparent from a study of this disclosure, the drawing and the appended claims.

According to this invention, there is provided an alkylation of anisoparafn with an olefin in the presence of hydrouoric acid'resulting'in an alkylate-containing effluent which is fractionated, deisobutanized, and deuorinated, which comprises the steps of passing the effluent to a deisoparanizer zone, removing normal' paralin from said Zone and circulating alkylate-containing fractionated alkylation effluent from said zone to a defluori- 23 into debutanizer 24. Normal butane is taken overhead Yfrom debutanizerl 24 by way of conduit 25 `and debutanized alkylate is sent to storage by way of` conduit 26. Although it is within the scope of this invention to take normal butane from conduit 14 to any desired place of utilization, in this example, it is passed to the debutanizer at a suitable place as will be understood by those skilled in the art of fractionation.

The residence time provided -in the defluorinator is accomplished by maintaining the ratio of Ifeed to the defluorinator to the net bottoms product at about 6-8 to 1. Thus, according to the combination of steps which constitute the essence of this invention, sulcient normal ibutane is taken o 'as a side stream by way of conduit 14 to permit elfective fractionation in deisobutanizer 12 to be eifected while at the sarne time maintaining the above-stated ratios. The stream in conduit 14 consists primarily of normal butane but it may contain some pentane and heavier. lIn this manner, the kettle product will contain only nominal amounts of butane and the correct residence time in the furnace is obtained. The pentane and heavier from the vapor side draw conduit 14 and kettle product can be recovered 4in the debutanizer according to practices known to one skilled in the art.

The location of vapor side stream conduit 14 is preferably at a point in the vapor space :above the fourth or the fifth tray from the bottom of the column, in a fractionating column employing conventional bubble trays or the like; however, the normal butane containing side stream can be withdrawn from the column vat .any tray fromv lance requirements of the deisobutanizer column. Total vaporization lalso increases any tendency of the materials being heated to form coke inthe reboiler coils.

The following example includes operating conditions Vand flow rates for a process according to the drawing.

Bblslstream P.p.m.

day

Feed to Deisobutanizer '7,098

Composition: F

Cs-l- Organic Fluoros Deisbutanizer Bottoms (alkylate prodllC A circulation rate is maintained through the reboiler of 18,00() BPSD. The material entering the reboiler has an organic iiuoride content of 300 ppm.

The operatingfconditions of the deisobutanizer are as follows:

Tempera- Pressure,

ture, F. p.s.i.a.

Top 150 18() Bottom 340 Reflux to deisobutanizer-6,975 BPSD.

The following conditions prevail in the dehutanizer. A 30 tray column with feed entering on fifteenth tray is used.

Bbls/stream Ppm,

day

Feed to Debutanizer 1, 878 Composition:

DEBUTANIZER BOTTOMS Composition:

C5 1, 525 C4 l on PRODUCT Composition:

C4 255 iCl 96 The operating conditions of the debutanizer `are as follows:

Tempera- Pressure,

ture, F. p.s.i.a.

Tcp 135 85 Bottom..- 315 As will be understood by those skilled in the art in possession-of this disclosure, the normal butane which is removed ythrough conduit 14 can be partly contained in the feed to the alkylation operation. To the extent nor- V3,004,085; l, l,

mal butane appears in the feed or in the eliiuent, the invention is operative to remove a suicient amount of the same to make deluor-ination possible at optimum irac tionation conditions in the deisobutanizer. Thus, it is immaterial from a viewpoint of the invention, as claimed, just what are the feeds so long as there is obtained a hydrocarbon which interferes with the deiluorination operation, which in the cas'e of the specific example described, has been normal butane.

Reasonable variation and modiiioation are possible within the scope of the foregoing disclosure, drawing and the appended claims to the invention, lthe essence of of which is that yin the deisobutanizing operation in which an HF-alkylate is .deisobutanized, there are practiced deliuorination by circulating the bottoms of the deisobutanizer through a heater and returning the same to the deisobutanizer while at the same time removing a suicient amount of normal butane from the deisobutanizer to obtain proper equilibrium-vaporization conditions suitable lfor effective fractionation.

I claim:

1. A method for the deisobutanization of yan HF-alkylate and its substantially simultaneous defluor'ination which comprises the steps in combinationA as follows: feeding an HF-alkylate to a deisobutanizing zone, removing isobutane yas overhead from said zone, removing normal butane as a side stream from said zone, removing bottoms from said zone, passing bottoms thus removed into a deiluorinating zone heated to a dell-uorinating temperature, returning thus-heated bottoms to the 'bottom of said deisobutanizer zone, and withdrawing a portion of the thus-heated bottoms -from the deisobutanizer zone as deisobutanized and deuorinated alkylate.

2. A method according to claim l wherein the ratio of feed to the deiluorinating zone to the net bottoms product from. the deisobutanizer zone is in the range of approximately 6 8 to 1.

3. A method -for the deisoparainization of an 4HF- alkylate and its substantial simultaneous deiluorination which comprises the steps in combination as Vifollows: feeding an HF-alkylate to a deisoparainizer zone, removing isoparati'in as overhead from said zone, removing normal paraffin as la side stream from said zone, removing bottoms fromsaid zone, passing bottoms thus removed into a deduorinating zone heated to a deiluorinating temperature, returning thus-heated bottoms to the bottom of said deisoparainizer zone, and withdrawing a portion of the thus-heated bottoms yfrom the deisoparahnizer zone as deisoparainzed and deuorinated alkylate.

4. A method for the deisobutanization of `an HF-alkylate and its substantially simultaneous deuorination which comprises the steps, in combination 1as follows: feeding an HF-alkylate to a deisooutanizing zone, removing isobutane as overhead from said zone, removing normal butane as a side stream from said Zone, removing bottoms from said zone, passing bottoms thus removed into a deuorin-ating zone heated to a deiluorinating temperature of `about 500 F., returning the thus-heated bottoms to the bottom of said deisobutanizer zone, circulating said bottoms into said defluorination Zone at a ratio in the range 6-l:1 of bottoms yielded lfrom said deisobutanizer zone, and withdrawing ya portion of the thusheated bottoms from the deisobutanizer zone as deisobutanized and deuorinated alkylate.

References Cited in the tile of this patent UNITED STATES PATENTS 2,397,085 Boedeker et al. Mar. 26, 1946 2,494,876 Frey Ian. 17, 1950 2,542,927 Kelley Feb. 20, 1951 2,759,032 Dixon Aug. 14, 1956 

1. A METHOD FOR THE DEISOBUTANIZATION OF AN HF-ALKYLATE AND ITS SUBSTANTIALLY SIMULTANEOUS DEFLUORINATION WHICH COMPRISES THE STEPS IN COMBINATION AS FOLLOWS: FEEDING AN HF-ALKYLATE TO A DESIOBUTANIZING ZONE, REMOVING ISOBUTANE AS OVERHEAD FROM SAID ZONE, REMOVING NORMAL BUTANE AS A SIDE STREAM FROM SAID ZONE, REMOVING NORBOTTOMS FROM SAID ZONE, PASSING BOTTOMS THUS REMOVED INTO A DEFLUORINATING ZONE HEATED TO A DEFLUORINATING TEMPERATURE, RETURNING THUS-HEATED BOTTOMS TO THE BOTTOM OF SAID DEISOBUTANIZER ZONE, AND WITHDRAWING A PORTION OF THE THUS-HEATED BOTTOMS FROM THE DEISOBUTANIZER ZONE AS DEISOBUTANIZED AND DEFLUORINATED ALKYLATE. 